Tip: You can use Lunar Magic's Overworld Layer 3 Editing system to edit or create your own layer 3 images (castle bricks, fish, rocks) and apply unique effects per level via the Layer 3 Bypass in the main editor.
An Ice Bro. It walks back and forth, occasionally hopping and periodically throwing two iceballs, which will disappear when they hit the ground. They will freeze and hurt Mario (both can be turned off independently of each other).
It throws an extended sprite iceball. The included ExtendedGetDrawInfo fixes a crash in PIXI's, so it is highly recommended you replace it with it. You have to put ExtendedBlockInteraction is the routines folder for the sprite to assemble.
Make sure to specify the extended sprite number of the iceball (extended/iceball.asm) from list.txt in the Ice Bro's ASM file (sprites/IceBro.asm)!